DACs are used to convert a digitally coded signal to an analog signal, or in conjunction with successive approximation circuitry as part of an analog-to-digital converter. DACs convert a digitally coded signal to an analog signal that is proportional to the digital signal. The analog signal can take on many different values depending on the resolution. The range of analog values is predetermined and corresponds to the range of digitally coded signals. DACs may employ a single resistor string comprised of equal resistance resistors. The resistor string has intermediate taps between adjacent resistors in the resistor string as well as between the resistor string and an energy source energizing the resistor string. Switches, coupled between respective intermediate taps and an output node, when turned on electrically couple the intermediate tap to the output node, and isolate the intermediate tap from the output node when turned off.
A digitally encoded signal is provided to a decoding/driver circuit. The decoding circuit decodes the digitally encoded signal and turns on the appropriate switch to conduct the voltage at its associated intermediate tap to the output. Typically only a single switch is turned on at a time, resulting in a single intermediate tap being coupled to the output. A monotonic input-output characteristic that is a staircase output voltage is derived from the resistor-division voltage at the intermediate taps. The magnitude of the incremental steps in the output voltage is the voltage drop across one of the resistors of the resistor string.